Androgen receptor gene CAG repeat length varies in a race-specific fashionin men without prostate cancer

Objectives. Preliminary studies suggest that black men have shorter androge n receptor CAG repeat length compared with non-Hispanic whites. Because dec reased CAG repeat length (in particular less than 20 repeats) may be associ ated with increased prostate cancer risk, these findings are potentially im portant in providing a hypothesis to explain the increased risk of prostate cancer in black men. Methods. CAG repeat length in the androgen receptor (exon one) was determin ed by a polymerase chain reaction method in 130 non-Hispanic white and 65 b lack men. All men had prostate-specific antigen levels less than 4 ng/mL an d normal digital rectal examinations. Men self-classified themselves into r acial categories by a standardized questionnaire. Results. For whites, the mean +/- SD, median, and range of CAG repeat lengt h were 21.0 +/- 3.0, 21, and 9 to 28, respectively. For blacks, the mean +/ - SD, median, and range of CAG repeat length were 19.0 +/- 3.0, 19, and 13 to 26, respectively. The mean and median CAG repeat length in blacks were s tatistically significantly shorter than in whites. Black men were twice as likely as whites to have fewer than 20 CAG repeats (56.9% versus 28.5%, P = 0.0001). Conclusions. These data unequivocally demonstrate that androgen receptor ge ne CAG repeat length varies in a race-specific manner in men without eviden ce of prostate cancer. (C) 1999, Elsevier Science Inc. All rights reserved.